This invention relates generally to turbine engines and, more particularly, to apparatus and methods for preventing stall in a compressor.
A turbine engine typically includes a fan in front of a core engine having, in serial flow relationship, a low pressure compressor, or a booster, and a high pressure compressor. The low pressure compressor and the high pressure compressor each include an inlet section and a discharge section.
During engine power reductions, the inlet section of the high pressure compressor may generate an airflow blockage resulting from a flow differential between airflow through the high pressure compressor inlet section and the airflow through the booster discharge section. The airflow blockage generates a back pressure in the booster which causes the booster operating line to migrate closer to a stall limit. Migration of the booster operating line closer to the stall limit restricts the operating range of the turbine engine because less air continues to flow through the booster.
If the booster stalls, loud banging noises and flames or smoke may be generated at the booster inlet and/or discharge section. A booster stall condition results in excessive wear, degradation of performance, and a reduction in engine reliability and durability. In order to compensate for booster stall, the booster is typically over constructed, leading to more parts that in turn make the booster, and the resulting engine, heavier.
Booster stall is mitigated in existing engines by the use of complex variable bleed doors, or valves, which open during unsteady airflow conditions and allow a portion of the booster airflow to bypass the high pressure compressor. However, the bleed doors may fail or malfunction due to the complexity of the doors and valves.
Accordingly, it would be desirable to provide efficient booster stall protection without the added complexity of variable bleed doors. Additionally, it would be desirable to provide improved reliability of booster stall protection.